First off, I'm not against open-carry laws, I'm against stupidity (and you are correct - we have stupid people carrying now, and there will be stupid people carrying openly, so there isn't going to be a major change in the percentage of stupid people carrying).
But the attitudes will change in those who are stupid - mark my words. Again, I'm not advocating any changes to laws, I'm just worried on how the public will perceive gun-owners after people purposely open-carry their guns with an "in-your-face" attitude, or start puffing out their chests like the gun is a license to be a badass and purposely looking for trouble, or use their guns as a political tool such as a protest, or "reveal-your-carry" in an anti-gun private businesses (keep in mind, I'm taking all of these examples from stories posted here as either happening in the news or being suggested by members).
I'm not making this up man. News stories of it happening in the other places make me think it will happen here. The fact the folks are suggesting doing annoying "look at my gun" crap here on this board makes me think it will happen here. Think about the number of NDs in normal carry situations. Now think about someone in a demonstration trying to prove something they shouldn't be proving doing something stupid and causing an ND - that would be disastrous for gun-owners (and that's just one of about 100 different ways the wrong attitude and something to prove combined with open-carry of a loaded handgun could go wrong).
I sincerely hope I'm completely wrong and nothing happens, but if the posts I've read here and the news stories I've read from other states are any indication, we're in for some growing-pains with Open Carry.
Even stupid people hate stupidity even though they are too stupid to know that they are practicing stupidity and think you are stupid for thinking that they are stupid.